A reconstruction technology of finite element meshes based on reversal engineering was applied to solve mesh penetration and separation in the finite element simulation for the divergent extrusion. The 3D numerical si...A reconstruction technology of finite element meshes based on reversal engineering was applied to solve mesh penetration and separation in the finite element simulation for the divergent extrusion. The 3D numerical simulation of the divergent extrusion process in- cluding the welding stage for complicated hollow sections was conducted. Based on the analysis of flowing behaviors, the flowing velocities of the alloy in portholes and near the welding planes were properly controlled through optimizing the expansion angle as well as porthole ar- eas and positions. After the die structure optimization, defects such as warp, wrist, and the wavelike are eliminated, which improves the sec- tion-forming quality. Meanwhile, the temperature distribution in the cross section is uniform. Especially, the temperature of the C-shape notch with a larger thickness is lower than that of other regions in the cross section, which is beneficial for balancing the alloy flowing velocity.展开更多
Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion(ECAE)in semi-solid isothermal treatment was investigated.The results show that with increasing semi-solid isothermal treatment te...Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion(ECAE)in semi-solid isothermal treatment was investigated.The results show that with increasing semi-solid isothermal treatment temperature,the α phase solid grain size of processed Mg-Al-Zn alloy by ECAE increases firstly due to coarsening of α phase solid grains,then decreases due to melting of α phase solid grains.With the increase of extrusion passes during ECAE,the α phase solid grain size in the following semi-solid isothermal treatment decreases.The α phase solid grain size of processed Mg-Al-Zn alloy by ECAE under route BC is the smallest,while the α phase solid grain size of processed material by ECAE under route A is the largest.The primary mechanism of spheroid formation depends on the melting of recrystallizing boundaries and diffusion of solute atoms in the semi-solid state.展开更多
To reduce defects, such as the shrinkage cavity and the surface cracks caused by non-homogeneous metal flow in extrusion process, an extrusion method was proposed by using a die with the guiding angle. Numerical simul...To reduce defects, such as the shrinkage cavity and the surface cracks caused by non-homogeneous metal flow in extrusion process, an extrusion method was proposed by using a die with the guiding angle. Numerical simulation and experiment were conducted to investigate the metal flow in this extrusion process. It is shown that the stress state at the bottom of the die is changed. The tendency to generate the dead zone is decreased by employing the guiding angle at the die entrance. The shrinkage cavity is reduced because the non-homogeneous metal flow at the final stage of extrusion is improved. The axial stress is decreased greatly so that the surface cracks caused by additional stress are avoided.展开更多
A recrystallization and partial melting(RAP) process was introduced to prepare the semi-solid 7075 aluminum alloy used for thixoforming. In order to obtain an ideal semi-solid microstructure, a series of extrusion exp...A recrystallization and partial melting(RAP) process was introduced to prepare the semi-solid 7075 aluminum alloy used for thixoforming. In order to obtain an ideal semi-solid microstructure, a series of extrusion experiments were conducted to comparatively investigate the optimum extrusion process parameters. Commercial 7075 Al alloy samples were firstly extruded with varying extrusion ratios below the recrystallization temperature followed by homogenization, then these samples were reheated to the semi-solid state and held in the range of 5 to 50 minutes. The experimental results show that varying process cause the difference in the deformation degree and microstructure for as-extruded samples, resulting in various semi-solid microstructure. It is verified that the formation of equiaxed grains in semi-solid microstructure depends on recrystallization behavior of extruded samples during partial melting. Both relative high extrusion temperature and low extrusion ratio lead to high volume fraction of recrystallized area, thus entirely equiaxed solid grains in semi-solid 7075 Al alloy samples can be obtained finally. In addition, Ostwald ripening was determined as the dominate coarsening mechanism of solid grains in semi-solid state for this 7075 Al alloy during the RAP route. The influence of predeformation on recrystallization behavior of this 7075 Al alloy was discussed in detail.展开更多
An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications.However, this process has a high production cost due to the need for investment of high-pressure machinery....An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications.However, this process has a high production cost due to the need for investment of high-pressure machinery.The objective of this work is to develop a new semi-solid extrusion process using semi-solid slurry at low solid fractions.A laboratory extrusion system was used to fabricate aluminum rods with the diameter of 12 mm.The semi-solid metal process used in this study was the gas induced semi-solid (GISS) technique.To study the feasibility of the GISS extrusion process, the effects of extrusion parameters such as plunger speed and solid fraction on the extrudability, microstructure, and mechanical properties of extruded samples were investigated.The results show that the plunger speed and solid fraction of the semi-solid metal need to be carefully controlled to produce complete extruded parts.展开更多
An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational accuracy.The method was implemented based on M...An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational accuracy.The method was implemented based on MSC/MARC by using a fractional step method,i.e.a Lagrangian step followed by an Euler step.The Lagrangian step was a pure updated Lagrangian calculation and the Euler step was performed using mesh smoothing and remapping scheme.Due to the extreme distortion of deformation domain,it was almost impossible to complete the whole simulation with only one mesh topology.Therefore,global remeshing combined with the ALE method was used in the simulation work.Based on the numerical model of the process,some deformation features of the sheet metal extrusion process,such as distribution of localized equivalent plastic strain,and shrinkage cavity,were revealed.Furthermore,the differences between conventional extrusion and sheet metal extrusion process were also analyzed.展开更多
Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts. However, there is still not enough know-how available. In this paper, as one of the typical sheet bu...Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts. However, there is still not enough know-how available. In this paper, as one of the typical sheet bulk metal forming processes, the sheet metal extrusion process was studied. A reasonable finite element method (FEM) model of sheet metal extrusion process taking the influence of flow-stress curve with wide range of plastic strain and ductile damage into consideration was established and simulated by an arbitrary Lagrangian-Eulerian (ALE) FEM implemented in MSC.Marc. Validated by comparing the results with experiment, some phenomenological characteristics, such as metal flow behavior, shrinkage cavity, and the influence of different combinations of diameter of punch, diameter of extrusion outlet, and diameter of pre-punched hole were analyzed and concluded, which can be used as theoretical fundamental for the design of the sheet metal extrusion process.展开更多
The methodology was used to conduct the upper bound analysis of thixotropic extrusion process of semi-solid metal. The calculated formulas of deformed power were derived. The relationship among relative stress, fricti...The methodology was used to conduct the upper bound analysis of thixotropic extrusion process of semi-solid metal. The calculated formulas of deformed power were derived. The relationship among relative stress, frictional factor and die semi-angle were obtained. The relative stress increases with increasing frictional factor, whose value increases with increasing area reduction ratio of a certain die semi-angle. The relative stress firstly decreases and then increases with increasing die semi-angle at a certain area reduction ratio. So, the optimal die semi-angle exists with the corresponding minimum relative stress. The calculated results are in agreement with the experimental ones, which are applied to directing technological practice of axis-symmetry forward extrusion of semi-solid magnesium alloys.展开更多
Shear-extrusion process and its forming parameters are proposed, whilst its laborsaving characteristic is utilized to forge large-size shutoff valve bodies on the middle-due press. This new process is intended for the...Shear-extrusion process and its forming parameters are proposed, whilst its laborsaving characteristic is utilized to forge large-size shutoff valve bodies on the middle-due press. This new process is intended for the manufacture of large-size forged tubular components with branches on the middle-due press. Experiments are carried out and processing parameters are obtained regarding the shear- extrusion process of a large-size shutoff valve body. Deformation and metal flow in the shear- extrusion process are investigated. In order to verify the laborsaving characteristic of this new process, some contrast experiments of extrusion force are performed between shear-extrusion and upsetting-extrusion for forming tubular components with branches. Based on rigid-plastic FEM, a plane-strain model is established to analyze shear-extrusion process of tubular components with branches. The analysis results by 2-dimensions FEM are comparatively well consistent with experimental results. Both simulated and experimental results show that this new forming process is feasible for forging large-size tubular components with branches on the middle-due press.展开更多
The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes...The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes increasing, the grains of the alloy are graduallyrefined and the hardness increases correspondingly. After ten passes of upsetting extrusionprocessing, the grain size decreases to less than 200 nm in diameter and the sample maintains itsoriginal shape, while the hardness is double owing to equal-axial ultrafine grains and workhardening effect caused by large plastic deformation.展开更多
This paper reviewed the trend and development of semi-solid metal technique. The processes and mechanisms for producing slurry of SSM and its industrial applications have been summarized and discussed. Discussions on ...This paper reviewed the trend and development of semi-solid metal technique. The processes and mechanisms for producing slurry of SSM and its industrial applications have been summarized and discussed. Discussions on the basic rheological theory are presented for more applications. Further consideration of the development and application of SSM technique is also proposed.展开更多
This study investigated the rheological properties of semi-solid metal. An analytical model of apparent viscosity was built up based on analysis of energy dissipation during rheological processes such as slurry prepar...This study investigated the rheological properties of semi-solid metal. An analytical model of apparent viscosity was built up based on analysis of energy dissipation during rheological processes such as slurry preparing, delivering and model filling. The rheological properties of SSM (semi-solid metal) slurry was described by an analytical model in terms of microstructural parameters, which consist of effective solid fraction, particle size and shape, and flow parameters such as mean velocity, fluctuant velocity and relative velocity between liquid and solid phase. The model was verified in the experiment of A356 alloys with a coaxial double-bucket rheometer. And the maximum relative error between the theoretical value and measured one is less than 20%. The results of experiment and theoretical calculation also indicate that the microstructural parameters and flow parameters are two major factors that affect the apparent viscosity of semi-solid alloys, and fluctuant velocity and relative velocity between liquid and solid phase are the key factors to distinguish between steady and transient rheological properties.展开更多
Tube and bar products of aluminum alloy composites reinforced by alumina short fiber were formed in a single process with liquid extrusion technology. The microstructure verifies that the reinforcing effect is obvious...Tube and bar products of aluminum alloy composites reinforced by alumina short fiber were formed in a single process with liquid extrusion technology. The microstructure verifies that the reinforcing effect is obvious in the deformation direction since fibers are distributed along this direction, which is resulted from the flow and crystallization under pressure of liquid metal and large plastic deformation of solidified metal in the process. The interface between fiber and matrix belongs to mechanical bonding. The fractograph demonstrates ductile mode. Liquid extrusion process opens up a new way for fabricating tube, bar and shaped products.展开更多
By optimizing formulation and fabrication methods, a new binder forplasticizing powder extrusion molding of hard metal, with excellent integrated properties anduniform distribution characters, has been developed. Ther...By optimizing formulation and fabrication methods, a new binder forplasticizing powder extrusion molding of hard metal, with excellent integrated properties anduniform distribution characters, has been developed. Thermal debonding mechanism and the extrudingtheological behaviours have been studied. The technology of fabrication of binder and thermaldebonding process have also been investigated. Using the novel binder, the hard-metalextrusion-molding rods with diameter up to 25mm, have been manufactured.展开更多
Despite the existence of conventional methods for recycling chips,solid-state techniques have become popular,whereby waste metals are directly recycled into consolidated products with the desired shapes and designs.We...Despite the existence of conventional methods for recycling chips,solid-state techniques have become popular,whereby waste metals are directly recycled into consolidated products with the desired shapes and designs.We investigated the feasibility of recycling phosphor bronze chips through a hot extrusion process using aluminum powder as a metal binder for the fabrication of a metal-fiber-reinforced aluminum matrix composite.To do so,mixtures containing 20 vol%–50 vol%of chips were prepared,cold-compacted,and extruded.The quality of the consolidated samples was evaluated by determining the density of the fabricated composites and studying their microstructures.In addition,we performed tensile and hardness tests to evaluate the mechanical properties of the fabricated composites.We also analyzed the fracture surfaces of the samples to study the fracture mechanism as a function of the volume fraction of phosphor bronze chips in the fabricated composite.The results indicated that the most effective consolidation occurred in the sample containing 20 vol%of chips extruded at 465℃in which the chips serve as ideal fibers for improving the mechanical properties,especially the ultimate tensile strength,in comparison with those of Al matrixes that contain no chips but are produced under the same conditions.展开更多
The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed i...The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed in deaerated 3.5%NaCl solution.In separate tests,the open-circuit potential was monitored in aerated 3.5% NaCl for 30 min after immersion.The electrochemical tests show that there is no significant difference in the pitting potential of the wrought alloys and that of the Cu-enriched surfaces of the SSM-HPDC alloys.展开更多
The shape control strategy of micro grooves is still unclear and challenging during the porthole die extrusion of grooved micro heat pipe(MHP).Through the simulation and experiment of porthole die extrusion of a MHP p...The shape control strategy of micro grooves is still unclear and challenging during the porthole die extrusion of grooved micro heat pipe(MHP).Through the simulation and experiment of porthole die extrusion of a MHP profile,the metal flow hysteresis behavior within micro features and the effect of ram speed and extrusion temperature on it and the resulting forming integrity was elucidated.Innovatively,Taguchi design and variance analysis(ANOVA)were introduced to determine their influence magnitude on the metal flow uniformity calculated by simulation results.The main findings are given below.The metal flow hysteresis derives from part feature size effect.The negligible friction-affected area during conventional extrusion severely slows down the metal flow within micro features during the MHP profile extrusion,which is due to the surge in the area ratio of the friction-affected area to the region in which it is located.Neither ram speed nor extrusion temperature can change the distribution of the friction-affected area.However,increasing ram speed multiplies the metal flow hysteresis and severely reduces the forming integrity,whereas extrusion temperature has little effect.Following this strategy,batch extrusion of the profile with microgrooved width of 0.27±0.02 mm was achieved in industrialized conditions.展开更多
文摘A reconstruction technology of finite element meshes based on reversal engineering was applied to solve mesh penetration and separation in the finite element simulation for the divergent extrusion. The 3D numerical simulation of the divergent extrusion process in- cluding the welding stage for complicated hollow sections was conducted. Based on the analysis of flowing behaviors, the flowing velocities of the alloy in portholes and near the welding planes were properly controlled through optimizing the expansion angle as well as porthole ar- eas and positions. After the die structure optimization, defects such as warp, wrist, and the wavelike are eliminated, which improves the sec- tion-forming quality. Meanwhile, the temperature distribution in the cross section is uniform. Especially, the temperature of the C-shape notch with a larger thickness is lower than that of other regions in the cross section, which is beneficial for balancing the alloy flowing velocity.
基金Projects(50475029,50605015) supported by the National Natural Science Foundation of China
文摘Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion(ECAE)in semi-solid isothermal treatment was investigated.The results show that with increasing semi-solid isothermal treatment temperature,the α phase solid grain size of processed Mg-Al-Zn alloy by ECAE increases firstly due to coarsening of α phase solid grains,then decreases due to melting of α phase solid grains.With the increase of extrusion passes during ECAE,the α phase solid grain size in the following semi-solid isothermal treatment decreases.The α phase solid grain size of processed Mg-Al-Zn alloy by ECAE under route BC is the smallest,while the α phase solid grain size of processed material by ECAE under route A is the largest.The primary mechanism of spheroid formation depends on the melting of recrystallizing boundaries and diffusion of solute atoms in the semi-solid state.
文摘To reduce defects, such as the shrinkage cavity and the surface cracks caused by non-homogeneous metal flow in extrusion process, an extrusion method was proposed by using a die with the guiding angle. Numerical simulation and experiment were conducted to investigate the metal flow in this extrusion process. It is shown that the stress state at the bottom of the die is changed. The tendency to generate the dead zone is decreased by employing the guiding angle at the die entrance. The shrinkage cavity is reduced because the non-homogeneous metal flow at the final stage of extrusion is improved. The axial stress is decreased greatly so that the surface cracks caused by additional stress are avoided.
基金Funded by the National Natural Science Foundation of China(Nos.51774054 and 51974050)
文摘A recrystallization and partial melting(RAP) process was introduced to prepare the semi-solid 7075 aluminum alloy used for thixoforming. In order to obtain an ideal semi-solid microstructure, a series of extrusion experiments were conducted to comparatively investigate the optimum extrusion process parameters. Commercial 7075 Al alloy samples were firstly extruded with varying extrusion ratios below the recrystallization temperature followed by homogenization, then these samples were reheated to the semi-solid state and held in the range of 5 to 50 minutes. The experimental results show that varying process cause the difference in the deformation degree and microstructure for as-extruded samples, resulting in various semi-solid microstructure. It is verified that the formation of equiaxed grains in semi-solid microstructure depends on recrystallization behavior of extruded samples during partial melting. Both relative high extrusion temperature and low extrusion ratio lead to high volume fraction of recrystallized area, thus entirely equiaxed solid grains in semi-solid 7075 Al alloy samples can be obtained finally. In addition, Ostwald ripening was determined as the dominate coarsening mechanism of solid grains in semi-solid state for this 7075 Al alloy during the RAP route. The influence of predeformation on recrystallization behavior of this 7075 Al alloy was discussed in detail.
基金the financial supports from Prince of Songkla University (Contract number AGR530031M)
文摘An aluminum extrusion process is mainly used to fabricate long tubes, beams and rods for various applications.However, this process has a high production cost due to the need for investment of high-pressure machinery.The objective of this work is to develop a new semi-solid extrusion process using semi-solid slurry at low solid fractions.A laboratory extrusion system was used to fabricate aluminum rods with the diameter of 12 mm.The semi-solid metal process used in this study was the gas induced semi-solid (GISS) technique.To study the feasibility of the GISS extrusion process, the effects of extrusion parameters such as plunger speed and solid fraction on the extrudability, microstructure, and mechanical properties of extruded samples were investigated.The results show that the plunger speed and solid fraction of the semi-solid metal need to be carefully controlled to produce complete extruded parts.
基金Project(50505027) supported by the National Natural Science Foundation of ChinaProject(20070248056) supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational accuracy.The method was implemented based on MSC/MARC by using a fractional step method,i.e.a Lagrangian step followed by an Euler step.The Lagrangian step was a pure updated Lagrangian calculation and the Euler step was performed using mesh smoothing and remapping scheme.Due to the extreme distortion of deformation domain,it was almost impossible to complete the whole simulation with only one mesh topology.Therefore,global remeshing combined with the ALE method was used in the simulation work.Based on the numerical model of the process,some deformation features of the sheet metal extrusion process,such as distribution of localized equivalent plastic strain,and shrinkage cavity,were revealed.Furthermore,the differences between conventional extrusion and sheet metal extrusion process were also analyzed.
基金supported by National Science & Technology Major Project of China (No. 2009ZX04014-073)National Natural Science Foundation of China (No. 50975175)
文摘Sheet bulk metal forming processes have been widely developed to the facilitate manufacture of complicated 3D parts. However, there is still not enough know-how available. In this paper, as one of the typical sheet bulk metal forming processes, the sheet metal extrusion process was studied. A reasonable finite element method (FEM) model of sheet metal extrusion process taking the influence of flow-stress curve with wide range of plastic strain and ductile damage into consideration was established and simulated by an arbitrary Lagrangian-Eulerian (ALE) FEM implemented in MSC.Marc. Validated by comparing the results with experiment, some phenomenological characteristics, such as metal flow behavior, shrinkage cavity, and the influence of different combinations of diameter of punch, diameter of extrusion outlet, and diameter of pre-punched hole were analyzed and concluded, which can be used as theoretical fundamental for the design of the sheet metal extrusion process.
文摘The methodology was used to conduct the upper bound analysis of thixotropic extrusion process of semi-solid metal. The calculated formulas of deformed power were derived. The relationship among relative stress, frictional factor and die semi-angle were obtained. The relative stress increases with increasing frictional factor, whose value increases with increasing area reduction ratio of a certain die semi-angle. The relative stress firstly decreases and then increases with increasing die semi-angle at a certain area reduction ratio. So, the optimal die semi-angle exists with the corresponding minimum relative stress. The calculated results are in agreement with the experimental ones, which are applied to directing technological practice of axis-symmetry forward extrusion of semi-solid magnesium alloys.
文摘Shear-extrusion process and its forming parameters are proposed, whilst its laborsaving characteristic is utilized to forge large-size shutoff valve bodies on the middle-due press. This new process is intended for the manufacture of large-size forged tubular components with branches on the middle-due press. Experiments are carried out and processing parameters are obtained regarding the shear- extrusion process of a large-size shutoff valve body. Deformation and metal flow in the shear- extrusion process are investigated. In order to verify the laborsaving characteristic of this new process, some contrast experiments of extrusion force are performed between shear-extrusion and upsetting-extrusion for forming tubular components with branches. Based on rigid-plastic FEM, a plane-strain model is established to analyze shear-extrusion process of tubular components with branches. The analysis results by 2-dimensions FEM are comparatively well consistent with experimental results. Both simulated and experimental results show that this new forming process is feasible for forging large-size tubular components with branches on the middle-due press.
基金This project is financially supported by the Natural Science Foundation (No. E5305293) of South China University of Technology.
文摘The microstructure and hardness of a 2024 aluminum alloy subjected tomulti-pass upsetting extrusion at ambient temperature were studied. Experimental results indicatedthat with the number of upsetting extrusion passes increasing, the grains of the alloy are graduallyrefined and the hardness increases correspondingly. After ten passes of upsetting extrusionprocessing, the grain size decreases to less than 200 nm in diameter and the sample maintains itsoriginal shape, while the hardness is double owing to equal-axial ultrafine grains and workhardening effect caused by large plastic deformation.
基金the National Natural Science foundation of China! (59995440)
文摘This paper reviewed the trend and development of semi-solid metal technique. The processes and mechanisms for producing slurry of SSM and its industrial applications have been summarized and discussed. Discussions on the basic rheological theory are presented for more applications. Further consideration of the development and application of SSM technique is also proposed.
文摘This study investigated the rheological properties of semi-solid metal. An analytical model of apparent viscosity was built up based on analysis of energy dissipation during rheological processes such as slurry preparing, delivering and model filling. The rheological properties of SSM (semi-solid metal) slurry was described by an analytical model in terms of microstructural parameters, which consist of effective solid fraction, particle size and shape, and flow parameters such as mean velocity, fluctuant velocity and relative velocity between liquid and solid phase. The model was verified in the experiment of A356 alloys with a coaxial double-bucket rheometer. And the maximum relative error between the theoretical value and measured one is less than 20%. The results of experiment and theoretical calculation also indicate that the microstructural parameters and flow parameters are two major factors that affect the apparent viscosity of semi-solid alloys, and fluctuant velocity and relative velocity between liquid and solid phase are the key factors to distinguish between steady and transient rheological properties.
文摘Tube and bar products of aluminum alloy composites reinforced by alumina short fiber were formed in a single process with liquid extrusion technology. The microstructure verifies that the reinforcing effect is obvious in the deformation direction since fibers are distributed along this direction, which is resulted from the flow and crystallization under pressure of liquid metal and large plastic deformation of solidified metal in the process. The interface between fiber and matrix belongs to mechanical bonding. The fractograph demonstrates ductile mode. Liquid extrusion process opens up a new way for fabricating tube, bar and shaped products.
基金This project is financially supported by the National Natural Science Foundation of China (No. 5964120,69971007)
文摘By optimizing formulation and fabrication methods, a new binder forplasticizing powder extrusion molding of hard metal, with excellent integrated properties anduniform distribution characters, has been developed. Thermal debonding mechanism and the extrudingtheological behaviours have been studied. The technology of fabrication of binder and thermaldebonding process have also been investigated. Using the novel binder, the hard-metalextrusion-molding rods with diameter up to 25mm, have been manufactured.
基金Shiraz University through grant number 97-GR-ENG-16。
文摘Despite the existence of conventional methods for recycling chips,solid-state techniques have become popular,whereby waste metals are directly recycled into consolidated products with the desired shapes and designs.We investigated the feasibility of recycling phosphor bronze chips through a hot extrusion process using aluminum powder as a metal binder for the fabrication of a metal-fiber-reinforced aluminum matrix composite.To do so,mixtures containing 20 vol%–50 vol%of chips were prepared,cold-compacted,and extruded.The quality of the consolidated samples was evaluated by determining the density of the fabricated composites and studying their microstructures.In addition,we performed tensile and hardness tests to evaluate the mechanical properties of the fabricated composites.We also analyzed the fracture surfaces of the samples to study the fracture mechanism as a function of the volume fraction of phosphor bronze chips in the fabricated composite.The results indicated that the most effective consolidation occurred in the sample containing 20 vol%of chips extruded at 465℃in which the chips serve as ideal fibers for improving the mechanical properties,especially the ultimate tensile strength,in comparison with those of Al matrixes that contain no chips but are produced under the same conditions.
文摘The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed in deaerated 3.5%NaCl solution.In separate tests,the open-circuit potential was monitored in aerated 3.5% NaCl for 30 min after immersion.The electrochemical tests show that there is no significant difference in the pitting potential of the wrought alloys and that of the Cu-enriched surfaces of the SSM-HPDC alloys.
基金co-supported by the National Natural Science Foundation of China (No. 51635005)the 111 Project (No. B18017)
文摘The shape control strategy of micro grooves is still unclear and challenging during the porthole die extrusion of grooved micro heat pipe(MHP).Through the simulation and experiment of porthole die extrusion of a MHP profile,the metal flow hysteresis behavior within micro features and the effect of ram speed and extrusion temperature on it and the resulting forming integrity was elucidated.Innovatively,Taguchi design and variance analysis(ANOVA)were introduced to determine their influence magnitude on the metal flow uniformity calculated by simulation results.The main findings are given below.The metal flow hysteresis derives from part feature size effect.The negligible friction-affected area during conventional extrusion severely slows down the metal flow within micro features during the MHP profile extrusion,which is due to the surge in the area ratio of the friction-affected area to the region in which it is located.Neither ram speed nor extrusion temperature can change the distribution of the friction-affected area.However,increasing ram speed multiplies the metal flow hysteresis and severely reduces the forming integrity,whereas extrusion temperature has little effect.Following this strategy,batch extrusion of the profile with microgrooved width of 0.27±0.02 mm was achieved in industrialized conditions.